Yes and No.
While a better D would absolutely help, we could have been 9-6 heading into the Jets game (with Hotrod starting and POs on the line) If we could have scored the last time we had the football vs Hawks and Fish.
Hotrod needs to come through in a couple of games like that or us to push through. Russell Wilson has to and he has the best D. Roger Staubach did it a lot and had great Ds too (Doomsday anyone?)
Even the great 2014 D needed late game offensive heroics to win 3 games (Bears, Lions, and Vikings).
We need both IMHO.